make the maxRasterImage size configurable

Author: zhuxingwei

Runtime/editor/window_config.cs

@@ -4,6 +4,8 @@ namespace Unity.UIWidgets.editor {
     public class WindowConfig {
         public readonly bool disableRasterCache;
 
+        public static float MaxRasterImageSize = 4096;
+
         static bool? _disableComputeBuffer = null;
 
         public static bool disableComputeBuffer {

Runtime/ui/renderer/compositeCanvas/flow/raster_cache.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Unity.UIWidgets.editor;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.ui;
 using UnityEngine;
@@ -228,8 +229,8 @@ static bool _canRasterizePicture(Picture picture) {
             }
 
             //https://forum.unity.com/threads/rendertexture-create-failed-rendertexture-too-big.58667/
-            if (picture.paintBounds.size.width > 4096 ||
-                picture.paintBounds.size.height > 4096) {
+            if (picture.paintBounds.size.width > WindowConfig.MaxRasterImageSize ||
+                picture.paintBounds.size.height > WindowConfig.MaxRasterImageSize) {
                 return false;
             }